In order to properly maintain the operation of a telephone system, it is desirable to monitor electrical characteristics, such as the loop resistance and DC balance, of the multi-wire subscriber line that connects customer-premises equipment to a central office switch.
Heretofore, these characteristics have been monitored by test equipment located at a central test site. The equipment requires service personnel at the customer premise, or some other location remote from the test site, in order to make connection, under direction from the test site, between the various leads which constitute the subscriber line and specified reference terminals, such as ground. The subject invention mitigates these requirements by employing test apparatus to effectuate the necessary connections between the TIP (T) and RING (R) leads at the customer premises under remote control from the test site.
In addition, it is ofttimes desirable to be able to isolate the central office line from the subscriber line so as to detect and determine the location of short-circuit conditions that may result from lightning surges or similar aberrant conditions.